Research And Implementation Of Soft PLC Ladder Logic Programming System

Programmable logic controller(PLC),as an alternative technology of relay system,is widely used in the field of industrial automation,greatly improving industrial production efficiency and reducing industrial production costs.Traditional hardware-based PLCs rely on dedicated integrated circuit boards,making it difficult to build an open hardware system and failing to meet the open development needs of CNC systems.Based on the above requirements,along with the popularity of PCs,soft PLC technology that uses software to emulate traditional hardware has been developed.Soft PLC technology has retained the traditional PLC function at the same time,has a number of advantages of the PC.The customization and implementation of the IEC61131-3 standard has greatly promoted the development of soft PLC technology.This paper designs and implements a set of soft PLC ladder programming system that conforms to IEC61131-3 standard.This article mainly completes the following job:(1)Compare the technical characteristics of traditional PLC technology and soft PLC technology,explain the background and research significance of soft PLC;introduce the research status of soft PLC at home and abroad;discuss the main research content of this paper.(2)Introduce the IEC61131-3 international standard and its ladder diagram language.Based on this,adopt the modular programming idea,gives a whole design for the system,and divide it into an edit module and a compilation module,gives the specific implementation block diagram of the two modules.(3)Design and implement the system's editing module.The editing module mainly includes the editor interface,the element of the ladder diagram,thedata structure of the ladder diagram,the saving and loading of the ladder diagram,the ladder diagram syntax,the logic check and so on.In the saving module of the ladder diagram,a method based on JSON format is proposed to save and load the ladder diagram program and configuration information,and the corresponding conversion algorithm and implementation flow chart are given.The example proves that the file volumeis greatly reduced.(4)Design and implement the system's compilation module.The compilation module mainly includes the conversion from the ladder diagram to the instruction list algorithm,and the conversion from the instruction list to the target code algorithm.In the ladder diagram to the instruction list algorithm conversion module,the traditional binary tree traversal algorithm has been improved,and the conversion of the ladder diagram is implemented,and the instruction list program is generated.Compared with the traditional binary tree traversal,the space complexity of the algorithm is greatly reduced.(5)Complete the software development of the soft PLC system and perform functional tests on the system.The test results show that the system is operating normally and the expected design results are achieved.